Electromagnetically coupled interconnect system architecture

ABSTRACT

An electromagnetic interconnect method and apparatus effects contactless, proximity connections between elements in an electronics system. Data to be communicated between elements in an electronic system are modulated into a carrier signal and transmitted contactlessly by electromagnetic coupling. The electromagnetic coupling may be directly between elements in the system or through an intermediary transmission medium.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to an electromagneticcontactless interconnect scheme for providing a communication pathbetween electronic components, such as integrated circuits, and/orelectrical systems and, in particular, to an electrical interconnectscheme in which the electronic elements are electromagnetically coupledto each other either directly or through an intermediate device, bycontactless proximity connections.

2. Description of Related Art

Integrated circuits and other elements of an electronics systemtypically communicate with one another through a wired interconnectionstructure. For example, in a data processing or computing system, aparallel wired interface, such as a bus, may link a microprocessor toother integrated circuits, such as memory integrated circuits, withinthe system. To communicate with one another, all of the integratedcircuits and other electronic elements of the system must be physicallyconnected, with a direct current (DC) path, to the wired interconnectionstructure. In other words, the integrated circuits and other electronicselements must make physical contact with the wired interconnectionstructure. Thereafter, the integrated circuits and other system elementscan send electronic signals to each other over the wired interconnectionstructure.

Generally, only one integrated circuit or system element sends signalson the wired interconnection structure at any given time, but allintegrated circuits and system elements typically monitor each signaltraveling on the wired interconnection structure. Usually, an integratedcircuit or system element ignores data conveyed on the wiredinterconnection structure unless the data is addressed to thatintegrated circuit or system element.

In a typical wired interconnection structure, each wired signal line isusually implemented by a separate trace on a printed circuit board orthe like. Drivers and receivers within each integrated circuit or systemelement transmit and receive signals conveyed on each line of the wiredinterconnection structure. The drivers and receivers do so by physicallycontacting the lines and thereby creating an electrical connection withthe lines. Such prior methods, however, have several disadvantages: theyare costly, they consume power, they can distort and attenuate highfrequency signals, and they often require large, capacitiveelectrostatic discharge (ESD) protection devices. In many high frequencyapplications, the signal distortion caused by the wired interconnectionstructure, rather than the speed of the integrated circuits or systemelements themselves, often limits the speed or data rate at which theintegrated circuits and system elements are able communicate with eachother.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus foreffecting contactless, proximity connections between elements in anelectronics system.

In one embodiment, a plurality of electronic components, such asintegrated circuits, are electromagnetically coupled to a transmissionline. A first electronic component modulates data to be sent to anotherelectronic component. The modulated data signal is communicated from thefirst electronic component to the transmission line and then from thetransmission line to the other electronic component by electromagneticcoupling, obviating the need for physical contact between eitherelectronic component and the transmission line. In other embodiments,electronic components, such as integrated circuits, areelectromagnetically coupled to each other directly, obviating the needfor an intermediary, such as a transmission line.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 illustrates an exemplary embodiment of the invention in whichintegrated circuits are electromagnetically coupled to a transmissionline.

FIG. 2 is a plan view illustrating the integrated circuits of FIG. 1 ona printed circuit board.

FIG. 3 is a partial, cross-sectional view of the integrated circuits andprinted circuit board of FIG. 2.

FIG. 4 illustrates a block diagram of an exemplary integrated circuitthat may correspond to the integrated circuit 14 of FIG. 1.

FIG. 5 illustrates an exemplary embodiment of the invention in whicheight integrated circuits are electromagnetically coupled to atransmission line.

FIGS. 6 a and 6 b illustrate exemplary transmitter and receiver circuitsthat may correspond to the transceiver 16 in FIG. 4.

FIG. 7 illustrates exemplary coupling characteristic data for anexemplary embodiment of the invention.

FIG. 8 illustrates a block diagram of an exemplary integrated circuitthat may correspond to an integrated circuit that may be used with aplurality of contactless interconnects of the invention.

FIG. 9 illustrates an exemplary embodiment of the invention in which aplurality of integrated circuits are each electromagnetically coupled toa plurality of transmission lines.

FIG. 10 is a cross-sectional view from FIG. 9.

FIG. 11 is a cross-sectional, side view of an embodiment of theinvention in which daughter cards are electromagnetically coupled to amother board.

FIG. 12 is a detailed cross-sectional view of the connector elements ofFIG. 11.

FIG. 13 illustrates an exemplary integrated circuit that may be used inthe embodiment of the invention illustrated in FIG. 14.

FIG. 14 illustrates a cross-sectional view of an exemplary embodiment ofthe invention in which a plurality of integrated circuits areelectromagnetically coupled to a ring bus structure.

FIG. 15 illustrates a cross-sectional view of an exemplary embodiment ofthe invention in which a plurality of stacked integrated circuits areelectromagnetically coupled.

FIG. 16 illustrates an exemplary embodiment of the invention in whichdual sides of an integrated circuit are electromagnetically coupled.

FIGS. 17 a-17 c illustrate exemplary embodiments of the invention inwhich two or more integrated circuits are directly electromagneticallycoupled.

FIG. 18 illustrates an exemplary embodiment of an integrated circuithaving a spiral electromagnetic coupler.

FIG. 19 illustrates an equivalent circuit diagram corresponding to FIG.18.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method and apparatus foreffecting contactless, proximity connections between elements in anelectronics system. (As used herein, “contactless” refers to a lack of adirect physical or mechanical contact through which electrons can flow,i.e., “contactless” means that direct electrical contact betweenconductors is not required.) The following describes exemplaryembodiments of the invention. The invention, however, is not limited tothe following exemplary embodiments or to the manner in which theexemplary embodiments operate or are described herein.

FIGS. 1 through 4 illustrate an exemplary embodiment of the invention.As shown in FIG. 1, an electronics system 10 includes a plurality ofintegrated circuits 14(1)-14(x) and a transmission line 22. As shown inFIG. 1, a transmission line typically includes return line 23. Asillustrated in FIGS. 2 and 3, the integrated circuits 14(1)-14(x) aremounted on a printed circuit board 21, and the transmission line 22 isembedded in the printed circuit board. Alternatively, transmission line22 may be located on a surface of the printed circuit board 21. Asillustrated in FIG. 1, the transmission line 22 is preferably terminatedin its characteristic impedance 27, 29 to reduce or eliminatereflections.

Integrated circuits 14(1)-14(x) may be any type of integrated circuit orelectronic circuit. For example, one or more of integrated circuits14(1)-14(x) may be without limitation a memory device, a microprocessor,a microcontroller, a digital logic device, an analog device, or anycombination of the foregoing. FIG. 4 illustrates a block diagram of anexemplary integrated circuit 14 that may be used with the presentinvention. Although not part of integrated circuit 14, transmission line22 is also shown in FIG. 4 for clarity and discussion purposes.

As shown in FIG. 4, integrated circuit 14 may include a logic circuit 12that implements the function of the integrated circuit. Integratedcircuit 14 may also include an input/output interface 15 for controllinginput and output of signals to and from the logic circuit 12. Suchsignals may be any type of analog or digital signals. For example, in adata processing or computing system, the signals may include, withoutlimitation, data signals, address signals, control signals, timingsignals, clock signals, and the like. As used herein, the terms “data”and “signals” are intended to include all such signals.

Each integrated circuit 14 may also include a radio frequency (RF)transceiver 16 and a small electromagnetic coupler 18. Preferably, theelectromagnetic coupler is sufficiently small that it can be formed onor within the integrated circuit using standard semiconductorfabrication techniques. Alternatively, the electromagnetic coupler 18could be fabricated as part of the semiconductor package. Thus, theelectromagnetic coupler is preferably smaller than a typicalsemiconductor die. In the embodiment illustrated in FIGS. 1-4,input/output interface 15 preferably provides a serial interface to thetransceiver 16, and transceiver 16 encodes the data received frominput/output interface 15 using any suitable RF modulation scheme.Nonexclusive examples of suitable RF modulation schemes includeamplitude modulation (AM), frequency modulation (FM), phase codemodulation (PCM), phase modulation (PM), or any combination of theforegoing. It is believed that modulation schemes used in modemtechnology may be particularly advantageous in the present invention.However, the specific design of the transceiver and the specificmodulation scheme are not critical to the invention, and any suitabletransceiver and modulation scheme may be used with the presentinvention.

Transceiver 16 provides the modulated signal to electromagnetic coupler18. Electromagnetic coupler 18 is preferably formed on or as part of theintegrated circuit 14. As shown in FIG. 4, one end of theelectromagnetic coupler 18 is preferably grounded but may bealternatively terminated with impedance 19 to obtain desired directionalcoupling, power, or distortion characteristics. Furthermore, theelectromagnetic coupler 18 may be terminated or connected to a referencevoltage other than ground or open-circuited.

Electromagnetic coupler 18 is disposed in proximity to transmission line22 so as to be electromagnetically coupled to transmission line 22.Preferably, electromagnetic couplers 18 are disposed withinapproximately ten millimeters of the transmission line 22. The inventionis not limited, however, to placement of any electromagnetic coupler 18within ten millimeters of the transmission line 22. Transmission line 22is typically embedded in or located on printed circuit board 21. Becauseelectromagnetic coupler 18 is electromagnetically coupled totransmission line 22, the modulated signal provided to electromagneticcoupler 18 by transceiver 16 induces a similar but attenuated signal inthe transmission line. A contactless communication path or channel isthus provided between integrated circuit 14 and transmission line 22.

The transmission line 22 may be any type of transmission line includingwithout limitation a microstrip line, a strip line, a twisted pair, acoaxial cable, a wire over ground, a waveguide, or any combination,hybrid, or modification of the foregoing. The specific design orimplementation of the transmission line 22 is not critical to theinvention, and indeed, any structure capable of beingelectromagnetically coupled with an electromagnetic coupler 18 andconducting or channeling a received signal may function as atransmission line 22 in the present invention.

Regardless of its specific implementation, the transmission line 22 ispreferably embedded within a printed circuit board 21. However, thetransmission line may be formed on or otherwise mounted to provide aninterconnect channel between electromagnetically coupled circuits. Asmentioned above, in order to prevent or minimize reflections, thetransmission line 22 is preferably terminated at one or both ends in itscharacteristic impedance 27, 29.

The printed circuit board 21 is preferably a typical printed circuitboard as commonly used in the electronics field. The design andcomposition of the printed circuit board 21, however, is not critical tothe invention and may be any substrate capable of supporting electroniccomponents and on which or within which transmission lines or conductorscan be attached or formed.

Modulated signals induced on transmission line 22 by one integratedcircuit 14(1) may be detected by another integrated circuit 14(x) in thesystem 10. That is, the modulated signal in transmission line 22 inducesa similar but attenuated signal in the electromagnetic coupler 18(x) ofthe other integrated circuit or circuits 14(x) whose electromagneticcouplers 18(x) are disposed in proximity to the transmission line 22 soas to be electromagnetically coupled to the transmission line.

Assuming that the integrated circuit is configured as illustrated inFIG. 4, a modulated signal sensed by an electromagnetic coupler 18 isdecoded (demodulated) by transceiver 16. The decoded data is thenprovided to input/output bus 15, which provides the data to logiccircuit 12.

It should be noted that coupling between an electromagnetic coupler 18and transmission line 22 can optionally be made directional byterminating the grounded end of the electromagnetic coupler 18 in thecharacteristic impedance 19 of the electromagnetic coupler, asillustrated in FIG. 4. Then, depending on which end of electromagneticcoupler 18 is terminated to ground (with the characteristic impedance 19as shown in FIG. 4) and which end is connected to transceiver 16,electromagnetic coupler 18 can induce an RF signal traveling only in onedirection along transmission line 22 and can receive an RF signaltraveling only in the opposite direction along transmission line 22.

For example, an electromagnetic wave traveling on transmission line 22such that its wave front first passes the grounded end of coupler 18 andthereafter passes the end of coupler 18 connected to transceiver 16 willgenerate a signal in coupler 18 that is detected by transceiver 16. Onthe other hand, an electromagnetic wave traveling in the oppositedirection along transmission line 22 will generate a wave in coupler 18that is dissipated by impedance 19; transceiver 16 will not detect sucha wave.

If impedance 19 is not present (e.g., coupler 18 is grounded oropen-circuited), the wave generated in coupler 18 would reflect off ofthe end of coupler 18 back into transceiver 16. Thus, without impedance19, waves traveling in either direction on transmission line 22 aredetected by transceiver 16.

Regardless of whether impedance 19 is present, electromagnetic wavesgenerated by the transmitter portion of transceiver 16 will propagatealong coupler 18 from the transceiver to the grounded end of thecoupler. The wave propagating along coupler 18 will cause a wave to begenerated in transmission line 22 in the same direction. If impedance 19is not present, the wave in coupler 19 will reflect off of the groundedend of coupler 18 and propagate back toward transceiver 16. Thereflected wave will generate a wave in transmission line 22 in the samedirection as the reflected wave. Thus, without impedance 19, waves willbe generated in transmission line 22 in both directions.

If, however, impedance 19 is present, the initial wave generated bycoupler 18 will not reflect along coupler 18 back toward transceiver 16.Rather, the initial wave will be dissipated by impedance 19. In such acase, a wave is generated in transmission line 22 in only one direction.Thus, if impedance 19 is present, the transmitter portion of transceiver16 will create waves in transmission line 22 in only one direction.

Directional coupling between coupler 18 and transmission line 22, asdiscussed above, may be advantageous when, for example, the logiccircuit 12 of integrated circuit 14(1) is a microprocessor, and thelogic circuits 12 of the other integrated circuit or circuits 14(x) arememories or other devices that communicate with the microprocessor butnot with one another. An example of such a case is discussed below withrespect to FIG. 5. In such a case, the electromagnetic coupler 18 ofintegrated circuit 14(1) may be oriented to transmit signals to theright on transmission line 22 and to receive signals traveling to theleft of transmission line 22. The electromagnetic couplers 18 ofintegrated circuit or circuits 14(x) would be oriented to transmitsignal to the left and to receive signals transmitted to the right. Suchdirectional coupling can limit the load drawn by integrated circuit orcircuits 14(x) when any one of those integrated circuits is transmittingto integrated circuit 14(1). Of course, coupling between anelectromagnetic coupler 18 and transmission line 22 can be madebi-directional by simply leaving electromagnetic coupler 18 opencircuited or grounded.

A simple, exemplary transceiver circuit is illustrated in FIGS. 6 a and6 b. FIG. 6 a illustrates an exemplary transmitter 300 portion of thecircuit, and FIG. 6 b illustrates an exemplary receiver 400 portion ofthe circuit. Data to be transmitted is input at terminal 302 of XOR gate306. A square wave carrier signal is input at terminal 304 of XOR gate306. The square wave carrier signal may be a system clock signal. Theoutput 308 of XOR gate 306 is a bipolar phase shift keying (BPSK)modulated signal containing both the data and the clock to betransmitted. Resistor 310 controls the amount of current that will flowthrough coupling loop 312. Coupling loop 312 radiates electromagneticenergy corresponding to the modulated signal, which, as discussed above,induces a similar but attenuated modulated signal in any other couplingloop or transmission line that is electromagnetically coupled tocoupling loop 312.

In the exemplary receiver circuit 400 illustrated in FIG. 6 b, anattenuated modulated signal is generated in coupling loop 402 bytransmission of the modulated signal by any other coupling loop ortransmission line electromagnetically coupled to coupling loop 402. Themodulated signal is amplified by amplifier 404. The amplified,modulated-signal 406 is demodulated by bit synchronizer 408. If bitsynchronizer 408 requires a phase-locked-loop circuit, it may befeasible to use the phase-locked-loop circuit that is typically found inmost integrated circuits. Bit synchronizer 408 outputs demodulated dataand clock signals from the modulated signal at output 410. In addition,if a system clock signal was used by a transmitter to modulate thetransmitted signal, the bit synchronizer clock output may also be usedas a system clock signal at output 412. Other bit synchronizer clockrecovery schemes may be used including without limitation delay lockloops and early-late discriminators.

It should be stressed that the above described transceiver design isexemplary only. The specific design of the transceiver is not criticalto the invention, and any suitable transceiver may be used with theinvention.

Thus, in accordance with the above described embodiment of theinvention, two or more integrated circuits in system 10 may communicatewith each other without requiring a direct electrical contact ofconductors. All or part of the path between an electromagnetic coupler18 on a first integrated circuit 14(1) and the electromagnetic coupler18 an another integrated circuit 14(x) may be referred to as acontactless communication channel or path.

FIG. 5 illustrates an exemplary electronics system 11 in which eightintegrated circuits 14(1) through 14(8) are electromagnetically coupledto transmission line 22. For example, the eight integrated circuits maybe a microprocessor 14(1) and seven memory devices 14(2)-14(7). Theeight integrated circuits 14(1) through 14(8) are mounted on a printedcircuit board (not shown in FIG. 5). Each of the electromagneticcouplers 18(1) through 18(8) are electromagnetically coupled totransmission line 22. The system 11 may be partially or fully shielded.Exemplary shielding configurations are described more fully below.

An exemplary manner in which system 11 may operate is as follows. Inthis example, integrated circuit 14(1), a microprocessor, wishes towrite data to integrated circuit 14(4), in this example, a memorydevice. To do so, integrated circuit 14(1) modulates the following: thedata to be written to the memory, a write command code, and an addressidentifying both the memory device 14(4) and the location within memorydevice 14(4) to which the data is to be written into a carrier signal.Because electromagnetic coupler 18(1) is electromagnetically coupled totransmission line 22, the modulated signal in electromagnetic coupler18(1) generates a similar, though attenuated signal, on the transmissionline, which in turn generates a similar, though still furtherattenuated, signal in each of the electromagnetic couplers 18(2) through18(8). In this manner, each of the other integrated circuits 14(2)through 14(8), all memory devices in this example, receives the data,write command, and the address transmitted by microprocessor 14(1).Because the address identifies memory device 14(4) as the intendedrecipient of the transmission, only memory device 14(4) keeps andprocesses the data. Of course, if the system implementation requireshigher data rates than a single channel can support, a multiplicity oftransmission lines and channels can be utilized.

Although not required in the present invention, shielding materials maybe disposed in electronics system 10 so as to partially or completelyshield the contactless communication channels or paths shown in FIGS.1-3 and described above.

For example, as illustrated in FIGS. 2 and 3, a shielding plane 38 mayshield the circuitry on the integrated circuit 14 from theelectromagnetic coupler 18. (FIG. 2 is a plan view of the plurality ofintegrated circuits 14(1)-14(x) of FIG. 1 mounted on an upper surface ofprinted circuit board 21, and FIG. 3 is a partial sectional elevationview of the printed circuit board 21 and integrated circuits 14(1) and14(x) of FIG. 2.) As shown in FIG. 3, the active circuit elements of theintegrated circuit (e.g., the logic circuit 12, the input/outputinterface 15, and the transceiver 16 illustrated in FIG. 4) arefabricated on a die 32 that includes a semiconductor substrate andvarious metalization and insulating layers formed thereon.

A shielding plane 38 is disposed between the circuitry on the die andthe electromagnetic coupler 18. The shielding plane may be any type ofconductive material suitable for absorbing or blocking electromagneticsignals. Insulating layers 34 and 36 may be formed on the die 32surrounding the shielding plane 38. In the exemplary embodiment of FIG.3, a via 39 in shielding plane 38 is provided for electricallyconnecting active circuitry on the integrated circuit 14 (e.g.,transceiver 16 of FIG. 4) with electromagnetic coupler 18. Although notrequired by the present invention, the shielding plane 38 may begrounded and may supply connections to ground to the electromagneticcoupler 16 or the integrated circuit 14. Alternatively, the shieldingplane 38 may be electrically connected to a voltage supply and providepower or a reference voltage to integrated circuit 14.

One or more shielding planes may also be provided in or on the printedcircuit board 21. For example, a shielding plane 46 may be embedded inor formed on printed circuit board 21 between the transmission line 22and the integrated circuit 14. As illustrated in the exemplaryembodiment of FIG. 3, one or more gaps or “windows” 50 in the shieldingplane 46 allow electromagnetic coupling through gap(s) 50 between theelectromagnetic coupler 18 and the transmission line 22. Again, theshielding plane 46 may be connected to ground, a reference voltage, orpower and used to provide ground connections, a reference voltage, orpower to the printed circuit board 21 or the integrated circuit 14.Shielding plane 38 may also act as a lid or cover for the gaps 50 thatprevent radiation from either the coupling loop 18 or the transmissionline 22 from affecting circuitry on the die.

Another shielding plane 48 may be provided within or on the printedcircuit board 21 such that the transmission line 22 is disposed betweenthe shielding plane 46 and the shielding plane 48. Again, theseshielding planes 46, 48 may be connected to ground, a reference voltage,or power and used to provide ground connections, the reference voltage,or power to the printed circuit board 21 or the integrated circuit 14.As shown in FIG. 3, insulating layers, such as layers 40, 41, 42, and43, may also be included in or on the printed circuit board 21.

Thus, the above described shielding planes partially shieldcommunication paths from an electromagnetic coupler 18 on one integratedcircuit 14 to the electromagnetic coupler 18 on another integratedcircuit. Additional shielding planes, traces, or wires may be disposedaround the communication path to more completely shield thecommunication path. For example, additional shielding could be providedaround transmission line 22 to more complete shield the transmissionline. In addition, shielding material may be disposed around electronicssystem 10 itself to fully or partially “close” the entire system.

Circuitry composing the transceiver may be fabricated on the integratedcircuit using standard semiconductor fabrication techniques. That is, itmay simply be designed and fabricated as another piece of the overallcircuitry composing the integrated circuit. Electromagnetic couplers andshielding planes may likewise be fabricated on or within the integratedcircuit using standard semiconductor fabrication techniques.

Many multiplexing, data exchange, and communication schemes andprotocols are known in the electronics fields, and any such scheme orschemes or combination thereof may be used with the above describedembodiment for transmitting data between integrated circuits. Forexample, known multiplexing schemes include without limitation timedivision multiplexing, frequency division multiplexing, and codedivision multiplexing. Exemplary, known protocols include withoutlimitation Scalable Coherent Interface (SCI), Fire Wire, Ethernet, andUniversal Serial Bus. Again, any such multiplexing scheme or protocol orcombination thereof may be used with the instant invention.

As is known, the amount of attenuation that occurs between a signal inan electromagnetic coupler 18 and the corresponding signal generated inthe transmission line 22 (or between a signal in the transmission line22 and the corresponding signal generated in the electromagnetic coupler18) can be readily designed into any variation of the embodiment of theinvention described above. The following is a nonexclusive list ofparameters that affect the amount of attenuation: the proximity of theelectromagnetic coupler 18 to the transmission line 22; the physicalorientation of the electromagnetic coupler 18 to the transmission line22; the length of the electromagnetic coupler 18 relative to thewavelength of the carrier signal; the shapes of the electromagneticcoupler 18 and the transmission line 22. Using these and otherparameters affecting coupling known to persons skilled in the field, theattenuation of signals wirelessly passed between the electromagneticcouplers 18 and the transmission line 22 can be preselected and designedinto the system 10.

It should be noted, however, that when electromagnetic couplers 18 of alarge number of integrated circuits 14 are tightly coupled (that is,coupled so as to reduce substantially the amount of attenuation) to atransmission line 22, each electromagnetic coupler draws a substantialamount of power from the RF signal as it travels along transmission line22 and the RF signal can become severely attenuated by the time itreaches an integrated circuit at the end of transmission line 22. Insuch a case, it is preferable to design electromagnetic couplers 18 tobe less tightly coupled to transmission line 22 so that they do not drawsubstantially more power than needed to permit an incoming RF signal tobe properly detected by transceivers 16. Thus, generally speaking, loosecoupling is preferred over tight coupling, particularly in systems wheremany devices share a common channel. However, in systems where only asmall number of devices are coupled together, tighter coupling may bedesired to reduce attenuation between devices and reduce undesirableradiation. For example, tighter coupling may be appropriate in systemshaving eight or fewer electronic devices electromagnetically coupled toa transmission line.

Table I below summarizes three link budget analysis applicable over abroad range of operating conditions for the embodiment illustrated inFIG. 3 above, given the following coupling, particularly in systemswhere many devices share a common channel. However, in systems whereonly a small number of devices are coupled together, tighter couplingmay be desired to reduce attenuation between devices and reduceundesirable radiation. For example, tighter coupling may be appropriatein systems having eight or fewer electronic devices electromagneticallycoupled to a transmission line.

Table I below summarizes three link budget analysis applicable over abroad range of operating conditions for the embodiment illustrated inFIG. 3 above, given the following exemplary parameters. A carrierfrequency in the range of 1-10 GHz is assumed, and electromagneticcouplers 18 are about 2-3 millimeters long and about 50 microns aboveshielding plane 46. Insulating layers 36 and 38 together are about 25microns thick. Transmission line 22 is about 150 micron wide, spacedabout 150 microns from shielding planes 46 and 48. It should be stressedthat the above dimensions are exemplary only and given as the frameworksetting for the below described exemplary link budget analyses. Theinvention is not limited in any way to the above described dimensions orthe below described operating ranges.

Exemplary case #1 through case #3 of table I represent decreasing systemcost and complexity at the expense of decreasing data rate performance.

The Noise power Ni in milliwatts is given by the formula:Ni=1000k Te B,

-   -   Where:        -   k=1.38×10⁻²³ Joules/Degree (Boltzmann's constant)        -   Te=(F−1)To            scheme in a modest implementation. More complex modulation            schemes and circuitry are capable of yielding higher bits/Hz            densities. Likewise, spread spectrum techniques can yield            lower bit/Hz densities while yielding lower bit error rates            at lower SNR ratios at the expense of additional system            complexity.

Exemplary case # 1 represents a link budget where the system transmittervoltage (e.g., transceiver 16 of FIG. 4) is 2.4 volts peak-to-peak intoa 50 ohm (+11.6 dBm), an 18 dB transmitting electromagnetic coupler 18loss is used, the receiving electromagnetic coupler 18 has an additional18 dB loss, and the Printed Circuit Board (PCB) and other system lossestotal 6 dB. In this case the desired link margin is 10 dB and thedesired signal to noise ratio (SNR) is 25 dB. A conservative receiverimplementation noise figure of 8 dB is assumed. Hence, the availablenoise bandwidth is over 10 GHz, corresponding to a 3 Giga-bit/second(Gb/sec) data rate at 0.3 bit per Hz of bandwidth. In this case, thesignal level power would not necessarily be a limiting factor of theimplementation.

Exemplary case # 2 represents a link budget where the transmittervoltage is reduced 6 dB to 1.2 volts peak-to-peak into a 50 ohms (+5.5dBm), along with a more lossy 22 dB transmitting electromagnetic coupler18, together with the receiving electromagnetic coupler 18 has,representing an additional 22 dB loss. The link margin of case # 2 hasbeen decreased to a still conservative value of 8 dB. The noise figureof the receiver implementation has been increased to 9 dB. This systemwould represent a more economical system to implement than the systemillustrated by case #1. In case #2, the available noise bandwidth is 1.6GHz, corresponding to a 480 Mb/second (Mb/sec) data rate assuming 0.3bit per Hz of bandwidth.

Exemplary case #3 further reduces the transmitter voltage to 0.63 voltspeak-to-peak (0 dBm) and further increases system implementation lossesand reduces the link margin of the systems illustrated in Cases #1 and#2 above. Case #3 is representative of an even lower cost implementationthat nonetheless supports a 81 Mb/sec data channel.

Together, exemplary cases #1 through #3 represent a broad range ofoperating conditions for various transmitter levels, receiverimplementations and signal bandwidths. Many operating conditions outsidethe range of values of Table I could be implemented by those skilled inthe art. TABLE I Units Case # 1 Case # 2 Case # 3 Voltage output ofvolts p—p 2.4 1.2 0.63 transmitter RMS voltage = volts rms 0.83 0.420.22 Vp—p/2.88 Transmitter output dBm 11.6 5.5 0.0 (milliwatts into 50ohms) Outgoing Coupling Loss dB 18 22 26 Incoming Coupling Loss dB 18 2226 PCB and other System dB 6 6 6 Losses RF Signal power at dBm −30 −44−58 receiver Desired link margin dB 10 8 6 Desired SNR dB 25 20 15 Noisepower budget dBm −65 −72 −79 Noise Figure Of receiver dB 8 9 10 NoiseFigure Of receiver ratio 6 8 10 (F) Equivalent Noise degree K 1965 25693330 Temperature Te = (F − 1) × 370 Available signal Hz 10.6E+9 1.6E+9270.8E+6 Bandwidth Bit Rate at 0.3 bit/Hz Mb/Sec 3,168 481 81 [BPSK]

FIG. 7 depicts the electromagnetic coupling attenuation in dB betweentwo 2.5 mm, 50 ohm microstrip traces over a shielding plane that isgrounded. One trace, representing an electromagnetic coupler 18 of theabove described embodiment, is driven with a signal generator (e.g.,transceiver 16 of FIG. 4) having an output impedance of 50 ohms andterminated with a 50 ohm resistor. The other trace, representingtransmission line 22 in the above described embodiment, is terminated atboth ends with 50 ohms of impedance. The spacing between the twomicrostrips is 0.05 mm (plot A) or 0.4 mm apart (plot B). Microstripmodeling was used for conservative and easy to model estimates ofcoupling; actual coupling values achievable with the broadsidestructures of this invention will yield less attenuation and/or smallerstructures.

Again, it must be stressed that the above dimensions are exemplary onlyand given as a framework for the sample data present in FIG. 7. Theinvention is not limited in any way to the above described dimensions orthe sample data presented in FIG. 7.

FIGS. 8-10 illustrate an alternative embodiment of an integrated circuitthat may be used in electronics system 10. As shown in FIG. 8, unlikethe integrated circuit illustrated in FIG. 4 which includes only onetransceiver, integrated circuit 60 includes a plurality of transceivers62(1)-62(x), each of which may be similar to the transceiver 16illustrated in FIG. 4. Like integrated circuit 14 in FIG. 4, integratedcircuit 60 may also include a logic circuit 12 and an input/outputinterface 64.

Generally speaking, integrated circuit 60 may be utilized in electronicssystem 10 in any manner that integrated circuit 14 of FIG. 4 isutilized. Integrated circuit 60, however, may be contactlessly coupledto as many transmission lines as it has transceivers 62.

FIG. 9 illustrates an exemplary configuration of an electronics system59 in which a plurality of integrated circuits 60(1)-60(x) each havefour transceivers 62. The plurality of integrated circuits 60(1)-60(x)are mounted on a surface 65 of a printed circuit board 66. Embeddedwithin the printed circuit board (and shown in dashed-outline form inFIG. 5) are four transmission lines 76. As discussed above, thetransmission lines 76 may alternatively be formed on the printed circuitboard 66. Each of the four electromagnetic couplers 68 on each of theplurality of integrated circuits 60(1)-60(x) is coupled to one of thetransmission lines 76. Preferably, each of electromagnetic couplers62(1)-62(x) are disposed within approximately five millimeters of theits corresponding transmission line 76. The invention is not limited,however, to placement of any electromagnetic coupler 62 within fivemillimeters of a transmission line 76. In this manner, transmissionlines 76 form a four-path, bus-like structure in which the plurality ofintegrated circuits 60(1)-60(x) can contactlessly communicate with eachother over the bus-like structure.

As described above, the contactless communication paths in electronicssystem 10 of FIG. 9 may optionally be fully or partially shielded. FIG.10 illustrates an exemplary embodiment with partial shielding of theelectronics system 59 illustrated in FIG. 9. As shown in FIG. 10, ashielding plane 69 shields the circuitry on integrated circuit 60 fromthe four electromagnetic couplers 68 of integrated circuit 60. Each ofthe four transceivers 62 in integrated circuit 60 are electricallyconnected to an electromagnetic coupler 68 on the integrated circuit 60through vias 67 extending though separate gaps in a shielding plane 69.Additional shielding may be provided by shielding planes or traces 80disposed between transmission lines 76, and still further shielding maybe provided by shielding planes 74 and 78, between which transmissionlines 76 are located as illustrated in FIG. 6. If shielding plane 74 isincluded, gaps 72 in shielding plane 74 between each electromagneticcoupler 68 and each transmission line 76 are included in shielding plane74. Integrated circuit 60 can then be positioned on printed circuitboard 66 so that its electromagnetic couplers 68 are electromagneticallycoupled to the transmission lines 76 through the gaps 72.

As with the embodiment illustrated in FIGS. 1-4 above, one or more ofthe shielding planes may be grounded and may supply ground connectionsto the integrated circuits 60 or the printed circuit board 66.Similarly, one or more of the shielding planes my be connected to apower supply and supply power or a reference voltage to the integratedcircuits 60 or the printed circuit board 66.

Although the embodiments of the invention described above contactlesslytransmit data between integrated circuits, the present invention is notlimited to the contactless transmission of signals between integratedcircuits. FIG. 11 illustrates an exemplary embodiment of an electronicssystem 79 in which signals are contactlessly transmitted betweenelements of an electronic system other than integrated circuits, namely,a daughter board and a mother board.

As shown in FIG. 11, a plurality of daughter boards 86(1)-86(x) arephysically mounted to a mother board 82. Conventional edge connectors 84may be used to mount the daughter boards 86(1)-86(x) to the mother board82. Each daughter card 86 includes a transmission line 90 embeddedwithin or located on the daughter card 86. Motherboard 82 also includesa transmission line 89, which preferably is embedded in the mother boardbut may alternatively be located on the mother board. The transmissionlines 90 of the daughter boards 86 are electrically connected toelectromagnetic couplers 92, which, when the daughter boards 86 aremounted to the mother board 82, are positioned in proximity to thetransmission line 89 in the mother board 82 such that theelectromagnetic couplers 92 of the daughter boards 86 areelectromagnetically coupled to the transmission line 89 of the motherboard 82. Preferably, an electromagnetic coupler 92 is disposed withinapproximately five millimeters of its corresponding transmission line90. The invention is not limited, however, to placement of anyelectromagnetic coupler 92 within five millimeters of a transmissionline 89. In this manner, daughter boards 86 can contactlesslycommunicate with mother board 86.

The contactless communications paths illustrated in FIG. 11 mayoptionally be partially or fully shielded. FIG. 12 shows a partial,sectional view of a daughter board 86 and mother board 82 andillustrates exemplary shielding that may be utilized to partially shieldthe embodiment illustrated in FIG. 11. As shown in FIG. 12, a shieldingplane or shielding via 202 may be disposed within daughter board 86 toshield the daughter card from electromagnetic coupler 92. The amount ofshielding, of course, depends, among other things, on the degree towhich the electromagnetic coupler 92 is surrounded by shielding materialand thereby electromagnetically isolated from other elements on thedaughter board 86. As with other embodiments described herein, personsskilled in the field will thus be able to adjust the degree by whichdaughter card 86 is shielded from electromagnetic coupler 92 byselective placement of shielding planes or materials aroundelectromagnetic coupler 92. In the example illustrated in FIG. 12,shielding plane 202 includes a gap 210 through which transmission line90 is electrically connected to electromagnetic coupler 92.

Transmission line 89 in mother board 82 may also be shielded. As shownin FIG. 12, transmission line 89 may be disposed between shieldingplanes 204 and 208. As also shown, shielding plane 204 includes a gap206 in proximity to electromagnetic coupler 92, allowing for acontactless communication path through the gap between electromagneticcoupler 92 and transmission line 89. Transmission line 89 may be morefully shielded by including additional shielding planes that more fullyenclose the transmission line. For example, additional shielding planesmay be included in front of the transmission line 89 and behind thetransmission line (from the perspective of FIG. 12). As discussed above,the shielding planes may be connected to power or ground to providepower or reference signals to the mother board 82 or daughter board 86.

Daughter boards 86 may include integrated circuits or other systemelements that are electromagnetically coupled to transmission line 90 inaccordance with the principles of the present invention. For example,daughter boards 86 may include configurations as described above withrespect to FIGS. 1-10. Alternatively, daughter boards 86 may includeintegrated circuits or other system elements that are conventionallycoupled via contact connections to transmission line 90. Of course,daughter boards 86 may include multiple traces 90, and the connectionsbetween each such trace and system elements on the daughter cards mayinclude a combination of contactless connections and conventionalcontact connections.

It should be noted that the present invention does not require thattransmission lines be arranged into any particular bus structure. FIGS.13 and 14 illustrate an exemplary embodiment of the invention thatutilizes a daisy-chain or ring type bus arrangement.

As shown in FIG. 13, an integrated circuit 90 may be configured with atransmitting coupler 102 and a separate receiving coupler 98 adapted forcommunicating through an electromagnetically coupled ring or token ringbus. Integrated circuit 90 may also include a logic circuit 92communicating via an input/output interface 94. A receiver 96demodulates an RF signal arriving on electromagnetic coupler 98 toproduce an input signal 95 to input/output interface 94. Typically, theinput signal 95 conveys data transmitted by another element that iselectromagnetically coupled to the ring bus. If the data is addressed tointegrated circuit 90, input/output interface 94 passes the data tologic circuit 93. Otherwise input/output interface 94 encodes the datainto an output signal 97 and passes it to transmitter 100. Transmitter100 supplies an RF signal modulated by the output signal 97 to anelectromagnetic coupler 102.

Input/output interface 94 also encodes any data originating from logiccircuit 93 to be sent to another element on the ring bus. Input/outputinterface 94 encodes the data along with the address of the intendedrecipient of the data and delivers an encoded output signal 97 totransmitter 100, which transmits the encoded signal onto the ring bus.

FIG. 14 is a simplified cross-sectional view of a printed circuit board104 holding several integrated circuits 90 similar to integrated circuit90 of FIG. 13. Separate short traces 106 embedded in or located on theprinted circuit board 104 electromagnetically couple pairs of couplers98 and 102 on adjacent integrated circuits 90. Shielding such as thatdiscussed above with respect to other embodiments of the invention mayalso be included. For example, a shielding plane 108 may shield traces106 from one another. Although not shown in FIG. 14, printed circuitboard 90 may also include shielding planes above and below traces 108,and integrated circuit 90 may include a shielding plane aboveelectromagnetic couplers 98 and 102 and below the circuits implementedon the substrate of integrated circuit 90 to provide shielding.

Although the above-described embodiments of the invention utilize atransmission line as an intermediary bus-like structure incommunications between integrated circuits, the present invention is notlimited to contactless transmissions involving a transmission line orany type of bus arrangement.

FIGS. 15-16 illustrate an exemplary embodiment of the invention in whichintegrated circuits contactlessly communicate directly with each other.As shown in FIG. 15 (a cross-sectional side view), a plurality (in thisexample three) of integrated circuits 112(1)-112(3) are verticallystacked. For example integrated circuit 112(3) might include a computerprocessor and integrated circuits 112(1) and 112(3) might implementmemories the processor accesses. Each integrated circuit 112(1)-112(3)includes a substrate 116 in which is formed circuitry. For example, thecircuitry might include a logic circuit, an input/output interface, anda transceiver or transceivers configured in an arrangement similar tothat of integrated circuit 14 of FIG. 4, integrated circuit 60 of FIG.8, or integrated circuit 90 of FIG. 13. The transceiver in eachintegrated circuit 112(1)-112(3) is connected to a correspondingelectromagnetic coupler 118(1)-118(3), which is preferably formed on orwithin substrate 116. Electromagnetic couplers 118(1)-118(3) are locatedin proximity with each other so as to be electromagnetically coupledwith one another. In this manner, integrated circuits 112(1)-112(3)communicate with each other contactlessly through the silicon withoutrequiring vias or conductive vertical elements to interconnect thestacked dice.

Integrated circuits 112(1)-112(3) can be disposed such that eachelectromagnetic coupler 118(1)-118(3) is electromagnetically coupled toall of the other electromagnetic couplers. Alternatively, the couplers118(1)-118(3) may be tuned and “tightly” coupled to act as resonatetransformers to pass RF signals vertically in either direction betweenelectromagnetic coupler 118(1) and 118(3) without minimum attenuation.In such arrangements, a transmission by one integrated circuit 118 wouldbe received and decoded by all of the other integrated circuits. Onlythe integrated circuit to which the transmission was addressed, however,would keep and process the data in the transmission.

Alternatively, each integrated circuit 112 could be disposed (and orshielded) such that its electromagnetic coupler 118 iselectromagnetically coupled only to the electromagnetic coupler of theintegrated circuit immediately above and/or below. A communicationsprotocol such as that described above with respect to FIGS. 13 and 14could be used. For example, upon receiving a transmission from aneighbor, an integrated circuit 118 decodes the destination address ofthe transmission. If the transmission is addressed to the integratedcircuit, the integrated circuit decodes and processes the data in thetransmission. If, however, the transmission is not addressed to theintegrated circuit, the integrated circuit forwards the transmission toits other neighbor.

Optional shielding may be included. For example, shielding planes 126may be included in integrated circuits 118(1)-118(3) to shield thecircuitry in each integrated circuit from electromagnetic couplers118(1)-118(3). If such shielding planes 126 are included, gaps 128 inthe planes should be included between electromagnetic couplers118(1)-118(3). Additional shielding may be included in accordance withthe shielding principles discussed above to provide more completeshielding.

As illustrated in FIG. 15, the stacked integrated circuits 112(1)-112(3)may optionally be mounted on a printed circuit board 114. The stackedintegrated circuits 112(1)-112(3) may make conventional physical contacttype electrical connections with printed circuit board 114.Alternatively, the stacked integrated circuits 112(1)-112(3) maycommunicate contactlessly with the printed circuit board 114. Such anarrangement is illustrated in FIG. 15. There the integrated circuit112(3) communicates contactlessly with the printed circuit board 114,and the printed circuit board includes optional shielding in accordancewith the shielding principles discussed above. As also illustrated inFIG. 15, power and ground connectors 115 may be included to providepower, ground, and reference voltage connections to the integratedcircuits 118(1)-118(3).

As shown, printed circuit board 114, which may be similar to printedcircuit board 21 of FIG. 3, includes a trace 120 disposed between twoshielding planes 122 and 124. The trace 120 may convey a radio frequencysignal to other electronic elements on the printed circuit board 114.Examples of other circuit elements include without limitation otherintegrated circuits or other stacks of integrated circuits. Theelectromagnetic coupler 118(3) of integrated circuit 112(3) resides inproximity to a gap 121 in optional shielding plane 122 so that coupler118(3) is electromagnetically coupled to trace 120. In accordance withthe shielding principles discussed above, additional shielding planes ormaterials may be included to more fully shield trace 120 and thecontactless communication path between electromagnetic coupler 118(3)and trace 120.

FIG. 16 illustrates an exemplary embodiment in which one portion of anintegrated circuit 130 communicates contactlessly with another portionof the integrated circuit. As illustrated, an integrated circuit 130 hascircuits formed on both top and bottom surfaces of its semiconductorsubstrate 132. The circuits may include logic circuits, input/outputinterface circuits, and a radio frequency transceivers in arrangementssimilar to that of integrated circuit 14 of FIG. 4, integrated circuit60 of FIG. 8, or integrated circuit 90 of FIG. 13. An electromagneticcoupler 134 is associated with circuitry on one side of the substrate132, and a second electromagnetic coupler 140 is associated withcircuitry on the other side of the substrate. In this manner, couplers134 and 140 are electromagnetically coupled so that the circuitry on oneside of the substrate 132 can contactlessly communicate with circuitryon the other side of the substrate.

Full or partial shielding may optionally be included in the embodimentillustrated in FIG. 15. For example, shielding planes 138 and 144 may beappropriately disposed to shield the integrated circuits on both sidesof the substrate 132 from the couplers 134, 140. Additional shieldingmay be included in accordance with the principles discussed above tomore fully shield the integrated circuits from the couplers 134, 140.Gaps are provided in the shielding as needed to allow couplers 134 and140 to couple electromagnetically to each other.

As with the “stacked” integrated circuit embodiment illustrated in FIG.15 above, the dual-sided embodiment illustrated in FIG. 16 may bemounted on a printed circuit board 146. As discussed above with regardto FIG. 15, conventional physical contact structures may be used tocommunicate with the printed circuit board 146, or contactlesslycoupling in accordance with the instant invention may be used. FIG. 16illustrates the later with optional shielding planes 302, 304 forshielding transmission line 148. Gap 306 is provided in shielding plane302 to allow coupler 140 to couple to transmission line 148. Asdiscussed above, additional shielding could be added to more fullyshield trace 148.

Although not shown in FIG. 16, power and ground connectors (such as 115in FIG. 15) may be included to provide power, ground, and referencevoltage connections to the integrated circuit 130. In addition, multipleintegrated circuits similar to integrated circuit 130 (with circuitryintegrated into both sides of a substrate) may be stacked as shown inFIG. 15.

Of course, two or more integrated circuits each having anelectromagnetic coupler may simply be disposed such that theirelectromagnetic couplers are in sufficient proximity that they areelectromagnetically coupled to each other. Preferably, electromagneticcouplers that are electromagnetically coupled to each other are disposedwithin approximately twenty-five millimeters of each other. Theinvention is not limited, however, to placement of any electromagneticcoupler within twenty-five millimeters of any other electromagneticcoupler.

FIGS. 17 a to 17 c illustrate exemplary arrangements in which two ormore integrated circuits are arranged with a direct wirelesscommunication path or channel between two or more integrated circuits.The integrated circuits may be mounted on a printed circuit board (notshown) or other substrate or frame suitable for securing integratedcircuits. In these exemplary arrangements, an electromagnetic coupler isformed on an outer edge of the integrated circuit. In FIG. 17 a,integrated circuits 600 and 604 are arranged such that they canwirelessly communicate with each other. In FIG. 17 b, three integratedcircuits 610, 614, 418 are arranged such that each is able to wirelesslycommunicate with the other. In FIG. 17 c, one integrated circuit 630includes four electromagnetic couplers, each arranged to beelectromagnetically coupled to one of integrated circuits 634-646.

In accordance with the shielding principles discussed above, shieldingmaterials may optionally be included and disposed so as to fully orpartially shield or “close” one or more contactless communicationschannels between the integrated circuits. For example, shieldingmaterial (not shown in FIGS. 17 a-17 c) may be placed between theelectromagnetic couplers 601, 602, 611, 612, 613, 660, 662, 664, 666,668, 670, 672, 674 and circuitry on any of the integrated circuits shownin FIGS. 17 a-17 c as generally described above. As illustrated in FIG.17 a, shielding planes or traces 606, 608 may also be disposed so as toshield the contactless communication path between two or more coupledelectromagnetic couplers 601, 602. Although not shown in FIG. 17 a,additional shielding planes or traces may be included above and below(from the perspective of FIG. 17 a) integrated circuits 600 and 604 tomore fully shield the contactless communication path between couplers601 and 606. Similarly, shielding material 620, 622 may be disposed toshield the contactless communication paths among couplers 611, 612, 613in FIG. 17 b, and additional shielding (not shown) may be included aboveand below (from the perspective of FIG. 17 b) the integrated circuits610, 614, 618 to more fully shield the paths. FIG. 17 c likewise showsexemplary shielding material 650 shielding the contactless communicationpath between couplers 660 and 662 from the contactless communicationpath between couplers 664 and 666. Shielding material 648, 654, 652similarly shields contactless communication paths between the followingpairs of couplers: 668 and 670, 672 and 674, and 650, 652. Additionalshielding material (not shown) could be placed above and below (from theperspective of FIG. 17 c) the coupling areas between adjacent couplersto more fully shield the contact communication paths.

Although the electromagnetic couplers illustrated in FIGS. 1-17 c areshown as being formed by straight line conductors, the couplers may beformed by conductors of any other shape including without limitationspirals. Indeed, the shape and size of the electromagnetic couplers canbe selected to cause predetermined levels of inductance and capacitanceso as to form tuned or resonate circuit or radio-frequency transformerstructures. Moreover, as described above with respect to integratedcircuits illustrated in FIGS. 1-16, electromagnetic couplers 601, 602,611, 612, 613, 660, 662, 664, 666, 668, 670, 672, 674 are preferablyformed on or within the integrated circuit using standard semiconductorfabrication techniques. Alternatively, the electromagnetic couplers canbe fabricated as part of the semiconductor package.

FIG. 18 illustrates an exemplary spiral coupler 404 formed on or withina semiconductor substrate 402. Also formed on the substrate istransceiver circuitry 406 and functional circuitry 408, which may besimilar to like circuits illustrated in FIGS. 4, 8, and 13. FIG. 19illustrates a circuit modeling equivalent impedances of the spiralcoupler 404 and the transceiver circuitry 406 and a transmission line(not shown in FIG. 18) or like coupler to which the spiral coupler 404is coupled. In FIG. 19, L1 and C1 represent the inductance andcapacitance of spiral conductor 404 and its connection path totransceiver circuitry 406; R1 represents the input or output impedanceof the transceiver circuitry 406; and L2 and C2 represent the inductanceand capacitance of the transmission line (not shown in FIG. 18) to whichthe spiral conductor 404 is coupled.

The spacing between spiral coupler 404 and the transmission line or likecoupler may be selected to provide a link coupling factor k in the rangeof slightly more than 0.0 to 1.0 Inductances L1 and L2 and capacitancesC1 and C2 may be sized to resonate at the frequency f_(c) of the RFcarrier signal as follows:f _(c)=1/[2PI(L 1 C 1)^(1/2)]=1/(2PI(L 2 C 2)^(1/2)]  [1]

The input impedance R1 of the transceiver to obtain a desired circuitquality factor Q as follows:Q=R 1/[(L 1 C 1)^(1/2)]  [2]

Higher values of Q increase the amount of coupling between the spiralcoupler 118 and the transmission line but also decrease RF signalbandwidth. The appropriate choice for Q thus depends on the amount ofsignal attenuation the transceivers can tolerate.

If tight coupling between electromagnetic couplers is desired, theelectromagnetic couplers may be one fourth of the wavelength of the RFsignal carrier frequency, thus forming a resonate coupling structure. Asnoted above, however, if electromagnetic couplers of a large number ofintegrated circuits are tightly coupled to a transmission line, eachelectromagnetic coupler draws a substantial amount of power from theradio frequency signal as it travels along the transmission line and theradio frequency signal can become severely attenuated by the time itreaches an integrated circuit at the end of a transmission line. Asdiscussed above, in such a case, it is preferable to sizeelectromagnetic couplers to be less tightly coupled to the transmissionline so that they do not draw substantially more power than needed topermit an incoming radio frequency signal to be properly detected by thetransceivers. Where only a few integrated circuits are contactlesslyconnected to each other, it may be advantageous to increase the couplingbetween integrated circuits to reduce the amount of radio-frequencyenergy radiated and hence reduce shielding requirements.

While the forgoing specification has described preferred embodiment(s)of the present invention, one skilled in the art may make manymodifications to the preferred embodiment without departing from theinvention in its broader aspects. For example, it should be understoodthat invention can be used in combination with conventional datacommunication techniques. For example, the electronics systems describedabove may also include integrated circuits and other system elementsthat communicate conventionally via physical contact. As anotherexample, any of the transceivers described above may be replaced with acircuit that only transmits or only receives as may be appropriate in agiven application of the invention. In addition, the input/outputinterface 15, 64, and 94 in FIGS. 4, 8, and 13, may be configured tocommunicate with other elements in addition to a transceiver and a logiccircuit. Also, in FIG. 3, integrated circuits 14 could be mounted onboth sides of the printed circuit board 21, and gaps provided inshielding plane 48 to allow couplers 18 on integrated circuits mountedon the lower (from the perspective of FIG. 3) of printed circuit board21 to electromagnetically couple with transmission line 22. Similarly,integrated circuits or stacks of integrated circuits could be mounted onboth sides of the printed circuit boards shown in FIGS. 10, 14, 15, and16.

1. (canceled)
 2. An electronics system comprising: a first integratedcircuit comprising a first electromagnetic coupler; and a secondintegrated circuit comprising a second electromagnetic coupler, whereinsaid first integrated circuit and said second integrated circuit aredisposed such that said first electromagnetic coupler is loosely coupledto said second electromagnetic coupler such that a signal in said firstelectromagnetic coupler induces a corresponding signal in said secondelectromagnetic coupler that is attenuated by at least about 10decibels.
 3. The electronics system of claim 2, wherein said firstelectromagnetic coupler is spaced no more than approximately tenmillimeters from said second electromagnetic coupler.
 4. The electronicssystem of claim 2 further including a substrate, wherein said firstintegrated circuit and said second integrated circuit are mounted tosaid substrate.
 5. The electronics system of claim 2 further including asubstrate, wherein said first integrated circuit is mounted to saidsubstrate and said second integrated circuit is mounted to said firstintegrated circuit.
 6. The electronics system of claim 2, wherein saidfirst electromagnetic coupler is smaller than said first integratedcircuit.
 7. The electronics system of claim 6, wherein said secondelectromagnetic coupler is smaller than said second integrated circuit.8. The electronics system of claim 2 further including shieldingmaterial disposed between circuitry on said first integrated circuit andsaid first electromagnetic coupler.
 9. The electronics system of claim 8further including shielding material disposed between circuitry on saidsecond integrated circuit and said second electromagnetic coupler. 10.The electronics system of claim 2 further including shielding materialdisposed to at least partially shield a contactless communicationchannel between said first electromagnetic coupler and said secondelectromagnetic coupler.
 11. The electronics system of claim 2 furthercomprising a third integrated circuit comprising a third electromagneticcoupler disposed to be electromagnetically coupled with at least one ofsaid first electromagnetic coupler and said second electromagneticcoupler.
 12. An electronics system comprising: a first integratedcircuit; a second integrated circuit; and electromagnetic coupling meansfor providing a loose, contactless electromagnetic coupling between saidfirst integrated circuit and said second integrated circuit such that asignal output by said first integrated circuit induces a correspondinginput signal in said second integrated circuit that is attenuated by atleast about 10 decibels.
 13. The electronics system of claim 12 furthercomprising first shielding means for shielding said first integratedcircuit.
 14. The electronics system of claim 13 further comprisingsecond shielding means for shielding said second integrated circuit. 15.An electronics system comprising: a first integrated circuit comprisinga first electromagnetic coupler; shielding material disposed betweencircuitry on said first integrated circuit and said firstelectromagnetic coupler; and a second integrated circuit comprising asecond electromagnetic coupler, said first integrated circuit and saidsecond integrated circuit dispose such that said first electromagneticcoupler and said second electromagnetic coupler are spaced from eachother but within sufficient proximity to be electromagnetically coupled,whereby data provided to said first electromagnetic coupler iscontactlessly communicated to said second electromagnetic coupler. 16.The electronics system of claim 15, wherein said first electromagneticcoupler is spaced no more than approximately ten millimeters from saidsecond electromagnetic coupler.
 17. The electronics system of claim 15further including a substrate, wherein said first integrated circuit andsaid second integrated circuit are mounted to said substrate.
 18. Theelectronics system of claim 15 further including a substrate, whereinsaid first integrated circuit is mounted to said substrate and saidsecond integrated circuit is mounted to said first integrated circuit.19. The electronics system of claim 15, wherein said firstelectromagnetic coupler is smaller than said first integrated circuit.20. The electronics system of claim 19, wherein said secondelectromagnetic coupler is smaller than said second integrated circuit.21. The electronics system of claim 15 further including shieldingmaterial disposed between circuitry on said second integrated circuitand said second electromagnetic coupler.
 22. The electronics system ofclaim 15 further including shielding material disposed to at leastpartially shield a contactless communication channel between said firstelectromagnetic coupler and said second electromagnetic coupler.
 23. Theelectronics system of claim 15 further comprising a third integratedcircuit comprising a third electromagnetic coupler disposed to beelectromagnetically coupled with at least one of said firstelectromagnetic coupler and said second electromagnetic coupler.